Varicella-zoster virus (VZV) is propagated in human embryonic lung fibroblasts. Viral DNA is subsequently prepared by isolation and extraction of VZV nucleocapsids. Varicella-zoster DNA is a linear double-stranded molecule of approximately 86 x 10 to the 6th power daltons molecular weight. The genome has been extensively studied by restriction endonuclease analysis and seems relatively stable during passage. Physical maps of the viral genome are being prepared. Preliminary experiments suggest that the genome exists in at least two isomeric forms and contains repetitive sequences. This will be further defined. VZV DNA is also being cloned in the plasmid vector pBR322. A library of sequences is now available and these cloned fragments are being employed as hybridization probes in the investigation of viral genomic organization, viral replication in vitro, viral latency in vivo, and possible viral oncogenicity. These techniques will also be used to study VZV strain variation and VZV gene function.